The word Celts is often used a lot to describe the ethnic groups of the British Isles, but where does it come from? Some people in the modern day culture wars say that the word “Celt” is a blanket term used by historical oppressors to lump everyone together, but this isn’t the intended purpose. Celtic was used by scholars in order to define a specific ethno-religious culture which spanned across Europe more than two thousand years ago and this was necessary instead of labeling an entire culture after a specific tribe. It would not suffice to call Celts “Helvitii” or “Boii” for example, therefore Celtic is the best way to describe the migration. The word Celt finds it’s oldest attestations in the annals of history from Greek and Roman writers in the Classic era. Indeed the word Kelt is not the only word that describe the Ethnic religious group that spanned all across Europe, but the word “Kelt” is undoubtedly a word used by those tribes themselves.
Modern Usage: A Revival of a Classical Word
It wasn’t until the 17th century that scholars such as Edward Lhuyd and Paul-Yves Pezron revived the term “Celt” to apply to the peoples of Britain and Ireland. Lhuyd, in particular, recognized that the languages spoken in Wales, Ireland, Scotland, and Brittany shared deep roots with the ancient Continental Celtic tongues, thus justifying the usage of the classical term.
Modern nationalism and antiquarianism cemented “Celt” as a pan-ethnic and cultural identity across the British Isles and beyond.
Keltoi
The first known use of the word Κελτοί (Keltoí) appears in the writings of Hecataeus of Miletus around c. 517 BCE. This early Greek geographer mentioned the Keltoi as a people living near Massilia (modern-day Marseille in southern France). This is the earliest recorded appearance of the term in the historical record, providing the first classical reference to what we now call the Celtic peoples.
Shortly thereafter, Herodotus, writing in the 5th century BCE, offers additional context. In Histories (Book II, 33), he places the Keltoi in a region “beyond the Pillars of Herakles,” near the source of the Danube River. This geographical reference situates them on the far western periphery of the known world to the Greeks, suggesting a somewhat vague and distant understanding of these peoples.
“Ἴστρος τε γὰρ ποταμὸς … ἀρξάμενος ἐκ Κελτῶν καὶ Πυρήνης πόλιος ῥέει …”
“For the river Ister begins from the Keltoi and the city of Pyrene and so runs that it divides Europe in the middle…”
— Herodotus, Histories 2.33 ( Macaulay translation )
Etymology: Where Did the Word Come From?
Despite centuries of usage, the origin of the word Keltoí remains debated. Several theories have been proposed:
- From PIE kʲel- – meaning “to hide,” possibly related to Old Irish ceilid (“he hides”).
- From kel- (“to impel, drive”) – related to the root behind “celerity.”
- From kʲel- meaning “to heat” or “be fierce.”
- As a Greek invention – coined by Greeks to describe a striking or towering group of foreigners, possibly meaning “the tall ones” (De Bernardo Stempel theory).
Regardless of origin, the word was not originally used by the Greeks to refer to the peoples of Britain or Ireland. Instead, it referred primarily to continental tribes, especially those in what is now France, Switzerland, southern Germany, and northern Italy.
Roman Usage and the Identification with Gauls
By the time of Julius Caesar in the 1st century BCE, the term Celtae had been adopted into Latin. In the opening line of his Commentarii de Bello Gallico, Caesar makes an important note regarding identity:
“Gallia est omnis divisa in partes tres… qui ipsorum lingua Celtae, nostra Galli appellantur.”
— De Bello Gallico I.1
(“All Gaul is divided into three parts… who in their own language are called the Celtae, in ours the Gauls.”)This passage is vital. It suggests that the Gauls themselves used Celtae as an endonym, or internal ethnonym, perhaps having adopted it from previous Greek usage or as a reflection of a pan-tribal identity that had formed under external pressure or influence.
Strabo, the Greek geographer writing around the turn of the millennium (1st century BCE to 1st century CE), also frequently refers to Celtica and distinguishes various Celtic-speaking groups, such as the Celtiberians of Hispania and the Celtici of Lusitania (in modern Portugal). His usage of Keltoí includes not just Gaul but stretches into Iberian territory, where Greek and Roman influence had encountered older tribal identities.
Pliny the Elder further confirms this in his Natural History (Book IV), referencing the Celtici as a tribal designation in Lusitania—adding to the body of classical sources that viewed the Celts as a wide-ranging group with shared cultural or linguistic traits.